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<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        
    </style>
</head>
<body>
    
</body>
<script>

    function Fn(){}
    function Fun(){}
    function Box(){}

    Fn.prototype = new Fun();

    const fn = new Fn();
    const fun = new Fun();
    const box = new Box();

    // fn 和 Fn        y
    console.log( Fn.prototype.isPrototypeOf( fn ) );
    console.log( fn instanceof Fn );
    
    // fun 和 Fn       n
    console.log( Fn.prototype.isPrototypeOf( fun ) );
    console.log( fun instanceof Fn );
    
    // fn 和 Fun       y
    console.log( Fun.prototype.isPrototypeOf( fn ) );
    console.log( fn instanceof Fun );
    
    // Fn 和 Fun       n
    console.log( Fn.prototype.isPrototypeOf( Fun ) );
    console.log( Fun instanceof Fn );
    console.log( Fn instanceof Fun );
    
    // fun 和 Fun      y
    console.log( Fun.prototype.isPrototypeOf( fun ) );
    
    // box 和 Box      y
    console.log( Box.prototype.isPrototypeOf( box ) );
    
    // fn 和 Object    y
    console.log( Object.prototype.isPrototypeOf( fn ) );
    
    // Fn 和 Object    y
    console.log( Object.prototype.isPrototypeOf( Fn ) );
    
    // Fun 和 Object   y
    console.log( Object.prototype.isPrototypeOf( Fun ) );
    
    // Box 和 Object   y
    console.log( Object.prototype.isPrototypeOf( Box ) );

    
</script>
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